The Hari River or Herat River (Persian هری رود Harī Rūd, i.e. "Herat River") is a river flowing 1,100 kilometres (680 mi) from the mountains of central Afghanistan to Turkmenistan, where it disappears in the Kara-Kum desert. Rud means "river" in Persian.

In Turkmenistan it is known as the Tejen or Tedzhen river and passes close to the city of Tedzhen.

To the Ancient Greeks it was known as the Arius.[1] In Latin, it was known as the Tarius.

Still some 200 kilometres (120 mi) upstream from Herat the river meets the Jam River at the site of the Minaret of Jam, the second tallest ancient minaret in the world at 65 metres (213 ft).

In western Afghanistan the Hari River flows to the south of Herat. The valley around Herat was historically famous for its fertility and dense cultivation. After Herat, the river turns northwest, then north, forming the northern part of the border between Afghanistan and Iran. Farther north it forms the south-eastern part of the border between Iran and Turkmenistan. The Iran–Turkmenistan Friendship Dam is on the river.

The Rigveda records the Harirud as River Sarayu.[3] The river Horayu is also mentioned in the Avesta.[4] A Buddhist monastery hand-carved in the bluff of the river Harirud existed in the first centuries during the prevalence of Buddhism. The artificial caves revealed testimony of daily life of the Buddhist monks.[5]